Laminated surface coverings for walls, ceilings, floors and furniture, such as counter, table and desk tops have been known for many years. These coverings are typically formed of polyvinylchloride as a homopolymer or copolymer, or some other resinous material such as polyurethane. To supplement the mechanical strength of the resins during processing and in the final product, such surface coverings generally incorporate a fibrous backing or interliner. The fibrous material employed for many years has been asbestos, which has set a standard for stability, strength and other physical and chemical properties, including the ability to retain dimensional stability over a wide range of temperature and moisture conditions. However, asbestos has been linked to serious health hazards and its use has been banned or severely limited in many countries.
A long list of fibrous materials have been suggested to be used alone or in combination in an effort to replace asbestos in backing and interliner sheets employed for this purpose. The various fibers have included polyolefins, polyesters, polyamides, or the like alone or in combination with glass fibers and wood pulp as well as other cellulosic fibers. To date, no composite employing any of these fibers, individually or in combination, has been able to provide a replacement material equivalent to a composite employing asbestos fibers.
The use of cellulosic fibers, such as wood pulp, as the sole fibrous component in the laminates and backing sheets has been suggested. However, sheets incorporating only cellulose fibers are subject to marked hygroexpansivity. The resulting product is often dimensionally unstable and swelling will often occur in the sheet and in any laminated surface covering in which the sheet is incorporated. A marked curl about the borders of the laminate and buckling between the lateral margins will also occur, sometimes resulting in the delamination of the backing sheet from the surface coverings.
To illustrate the significance of dimensional stability, surface coverings must be capable of use in a wide variety of climatic conditions, particularly humidity and temperature. These surface coverings are applied to walls, floors, and other substrates, using adhesives. The alignment and abutment of contiguous segments of surface covering must remain in registry after application. Any expansion or contraction of the backing sheet may result in delamination from the surface coating which is typically a stable vinyl layer. In extreme cases, this may result in the separation of the laminate from the surface of the floor or wall to which the laminate has been applied.
A method in which standard papermaking apparatus could be employed in the manufacture of a material for use as a backing sheet or interliner that would be dimensionally stable and substantially resistant to delamination would be particularly useful. If, in addition, the material also exhibited a high internal bond and did not become brittle and, further, exhibited the physical properties of a material incorporating asbestos fibers, it would also represent a significant step forward in the art.